Register mark dtection apparatus

Abstract

A register mark detecting apparatus detects a transparent register mark printed on a conveyed transparent web. The register mark detecting apparatus includes a light source, a parallel light flux irradiation optical system, a collective optical system, a knife-edge, and a light receiving element. The parallel light flux irradiation optical system converts a light flux from the light source into a parallel light flux to irradiate a transparent web with the parallel light flux. The collective optical system collects the light flux transmitted through the transparent web. The knife-edge is disposed near a back focus of the collective optical system. The knife-edge interrupts the light flux going straight in the transparent web and causes only the light flux refracted by being transmitted through the transparent register mark to pass by. The light receiving element receives the light flux transmitted through the knife-edge.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is the U.S. National Stage of International Patent Application No. PCT / JP2009 / 000620, filed on Feb. 17, 2009, which claims priority to Japanese Application No. 2008-055498 filed on Mar. 5, 2008, the disclosure of which is incorporated herein by reference.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to a register mark detecting apparatus that can detect a transparent register mark printed in invisible ink on conveyed transparent web.[0004]2. Description of the Related Art[0005]When a multicolor pattern is printed on transparent web with a rotary printing machine, usually color patterns are overprinted one by one to form one pattern. At this point, when the color pattern is superimposed, sometimes pattern misalignment is generated or a white space is generated between the colors. Therefore, it is necessary that alignment be correctly performed such that register deviation is ...

AI Technical Summary

Benefits of technology

[0012]Accordingly, when the transparent register mark is irradiated with the parallel light flux by the irradiation device, the light flux is incident to the light receiving device, so that the transparent register mark can be detected. Because the refraction caused by optical unevenness of the transparent register mark is utilized in the register mark detecting apparatus, the transparent register mark can be detected without adding additives such as a fluorescent bleaching agent and an ultraviolet absorber to the invisible ink. Accordingly, the appearance of the printed material is not adversely affected. Further, because the visible light source is used, the cost of the apparatus can be reduced.

[0013]The register mark detecting apparatus in accordance with the aspect of the invention may further include knife-edge moving device for moving the knife-edge. In the register mark detecting apparatus in accordance with the aspect of the invention, the knife-edge moving device may move the knife-edge to a position retracted from a back focus of the collective device so as not to interrupt the light flux going straight in the transparent web, when a visible register mark printed in visible ink is detected.

[0014]In such cases, the visible register mark printed in visible ink can be detected by retracting the knife-edge from the back focus of the collective device. The register mark detecting apparatus acts as both the visible register mark detecting apparatus and the transparent register mark detecting apparatus, so that the apparatus can be simplified to reduce the cost.

Problems solved by technology

On the other hand, in the case of the register mark printed in invisible ink, the register mark is hardly stably detected because a small difference in light quantity between the light transmitted through the register mark and the light transmitted through a portion in which the register mark is not printed.

However, in case where additives such as a fluorescent bleaching agent and an ultraviolet absorber are added to the invisible ink like Patent Documents 1 and 2, possibly an appearance of a printed paper is adversely affected.

Because the use of the light source emitting the ultraviolet light is required, cost of the apparatus is increased compared with the use of the visible light source.

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